Open the stl into a slicer and slice it. 

If using repetier then velocity painting is an option in the menu bar under tools. Add the gcode and the jpg into the parameters. After this you will be prompted to save a file name and generate the new vp'd gcode. If when it loads back into repetier, you find it unable to preview(as is my case) then download the app from github and it will have almost the same interface. Same process but the program needs to be closed before you can reopen it in repetier. Goodluck. Message me @theplasticowboy on twitter if you have any  issues.

#Velocitypainting is wonderful! I designed this simple vase / lamp shape in #tinkercad and applied an inverted jpg with #velocitypainting.  I prefer Mark Wheadon"s app  over the Repetier extension, currently,  due to not being able to properly preview  the  modified gcode before printing( it is beta, after all).  Printed on a Tevo Tarantula with an .8mm nozzle at .2mm layer heights.  #Makergeeks crystal series PLA - translucent green and #Orbpolymer's copperhead PLA. sliced  as a Spiralized contour or vase mode-(1 shell).

This prints out to 200mm wide by 160 mm tall so make sure it is centered  and that you have the clearance on your print bed. 

It is sliced and ready to print BUT !!! - You need to get familiar with #Velocity painting (luvit luvit luvit)- speed parameters and fan settings must be changed to  be harmonious. 

For more on those settings, please refer to  

https://github.com/MarkWheadon...

www.velocitypainting.xyz/blog/ 

https://www.repetier.com/veloc...

https://github.com/MarkWheadon...

https://www.reddit.com/r/3Dpri...

Plasticowboy

R. E. B.